Rapeseed meal (RSM) is a common protein ingredient in animal diets, while the proportion of RSM in diets is limited because of its anti-nutritional factors. Fermentation based on mixed microbial strains appears to be a suitable approach to improve the nutritive value of rapeseed meal in animal feed. In this study, we evaluated the effects of fermentation on the apparent metabolizable energy (AME) values and standardized ileal digestibility (SID) of amino acids in RSM fed broilers. The AME and nitrogen-corrected apparent metabolizable energy (AMEn) values of RSM and fermented rapeseed meal (FRSM) were determined by the substitution method, with RSM and FRSM proportionally replacing the energy-yielding components of the basal diet by 30%. Results show that fermentation improved AME and AMEn of RSM from 7.44 to 8.51 MJ/kg and from 7.17 to 8.26 MJ/kg, respectively. In the second experiment, two experimental diets were formulated, with RSM and FRSM being the sole sources of amino acids. A nitrogen-free diet (NFD) was also formulated to determine endogenous amino acids losses (EAAL). Feeding on FRSM resulted in higher (p < 0.05) apparent ileal digestibility (AID) and SID of alanine, valine, isoleucine, leucine, tyrosine, lysine, arginine, and phenylalanine. No significant differences between RSM and FRSM were found for AID and SID of asparagine, histidine, threonine, serine, glutamine, praline, glycine, methionine, and cystine. FRSM had greater AMEn values and SID of amino acids compared to RSM, therefore, FRSM was nutritionally superior to RSM in broiler diets.

Exogenous proteases are promising to stimulate the application of low-protein diets for broilers. A total of 540 1-day-old Arbor Acres male broilers were randomly assigned to 9 groups with 6 replicates of 10 birds. A 3 × 3 factorial, completely randomized arrangement was used to evaluate the effects of dietary crude protein (CP) and protease levels on growth and slaughter performance, immunity capacity, and apparent ileal digestibility (AID) of amino acids (AA). Dietary CP levels were 20.0%, 19.5%, or 19.0% during the starter phase, and 18.0%, 17.5%, or 17.0% during the finisher phase. Protease levels were 0, 250, or 500 mg/kg in diets throughout the trial. The trial lasted for 42 days. Weight gain and feed efficiency of broilers decreased as dietary CP lowered, but improved with protease supplementation. Dietary CP and protease levels had few effects and interactions on carcass characteristics, immune organ indexes, and immunoglobulin concentrations. The AID of most AA was improved by dietary CP decrease or protease supplementation. In conclusion, reducing dietary CP decreased the performance and immune capacity of broilers but increased the AID of AA. Almost independent of dietary CP level, dietary protease addition improved the performance of broilers, probably through the enhancement of AA digestibility, and had no effect on carcass traits.

This study aimed to investigate the impact of dietary supplementation with Moringa oleifera leaf powder (MOLP) on the growth performance, digestive enzyme activity, meat quality, and cecum microbiota of Ningdu yellow chickens. A total of 300 78-day-old Ningdu yellow chickens with similar initial body weights were randomly distributed into five treatments consisting of six replicates of 10 birds. The control group (M0) was fed a basal diet, and the experimental groups were fed diets supplemented with 0.5% (M0.5), 1% (M1), 2% (M2), and 4% (M4) of MOLP, respectively. Our results showed that dietary supplementation with 2% MOLP significantly (p < 0.05) decreased the feed to gain (F/G) and showed a quadratic (p < 0.05) decrease with the level of MOLP. Dietary supplementation with 1~4% MOLP resulted in a significant increase (p < 0.05) in serum total superoxide dismutase (T-SOD) activity and total antioxidant capacity (T-AOC). Furthermore, both serum T-SOD and T-AOC exhibited linear and quadratic increases (p < 0.01) in response to the supplementation with MOLP in the diets. Dietary supplementation with 1~4% MOLP significantly (p < 0.05) decreased serum uric acid (UA) level. Additionally, 4% MOLP significantly (p < 0.05) decreased triglycerides (TG), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels, and showed linear and quadratic effects. The activity of lipase in the duodenum showed a linear decreasing trend (p < 0.05) with the level of MOLP, while the activities of α-amylase (both in duodenum and jejunum) showed a linear and quadratic increasing trend (p < 0.05). In addition, there was a linear decrease response in abdominal fat (p < 0.05) to MOLP supplementation levels in the diets. In terms of meat quality, dietary supplementation with 4% MOLP significantly reduced (p < 0.05) the L*45 min and L*24 h values of the breast muscle, and drip loss had a linear decreasing trend (p < 0.05). In terms of cecum microbiota, dietary supplementation with 1~4% MOLP significantly increased the Bacteroidota abundance but decreased the Firmicutes abundance (p < 0.05). Overall, dietary supplementation with MOLP improved the growth performance and meat quality of Ningdu yellow chickens through improving the antioxidant function, intestinal digestive enzyme activity, and the cecal microbial structure. The optimum level of MOLP in the diet of Nindu yellow chicken is recommended to be 2.59%.

This study aimed to investigate the effects of dietary supplementation with 5-aminolevulinic acid (5-ALA) on growth performance, blood parameters, iron status, nutrient digestibility, and antioxidant capacity in broilers. A total of 600 one-day-old Arbour Acres broilers were distributed into 5 groups with 6 replicates of 20 birds by a completely randomised design. The birds in the 5 groups were fed the basal diets with 0, 15, 30, 45, and 60 mg/kg 5-ALA, respectively. Dietary supplementation with 60 mg/kg 5-ALA significantly reduced the feed to gain ratio during days 1–21 and days 22–42. Moreover, compared with the control group, dietary supplementation with 30 mg/kg 5-ALA elevated haemoglobin concentrations during days 1–21. Furthermore, dietary supplementation with 45 and 60 mg/kg 5-ALA increased the digestibility of crude protein and decreased serum uric acid levels. At 21 days of age, dietary supplementation with 45 and 60 mg/kg 5-ALA increased liver catalase activity and decreased liver malondialdehyde concentrations, and upregulated the liver mRNA expression of ferritin light chain and nuclear factor erythroid 2-related 2. In addition, the liver mRNA expression of haem oxygenase-1 and divalent metal transporter were upregulated in the 60 mg/kg 5-ALA supplementation group, while the liver mRNA expression of Kelch-like ECH-associated protein 1 was decreased in the 5-ALA supplementation groups. In conclusion, dietary supplementation with 60 mg/kg 5-ALA improved the growth performance, nutrient digestibility, iron status and antioxidant capacity of 21-d-old broilers.

This study evaluated changes in nutritional components and antinutritional factors in rapeseed meal before and after microbial fermentation. It further investigated the enhancements in its nutritional value and the growth-promoting effects of fermented rapeseed meal on broiler chickens. A total of 180 one-day-old male Arbor Acres (AA) broilers were randomly allocated into 3 treatment groups, with 6 replicates per group and 10 birds per replicate. The broilers were fed a basal diet (CON), a diet with 5% soybean meal (SBM) replaced by RSM (RSM-5), or a diet with 5% SBM replaced by FRSM (FRSM-5). The date of the experiment was 28 June 2025. The results showed that FRSM improves protein quality and reduces the levels of antinutritional factors, including glucosinolates (GSL), phytic acid (PA), and condensed tannins (CT), compared with unfermented RSM. Additionally, FRSM enhances antioxidant capacity in vitro, significantly enhancing the scavenging rates of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, hydroxyl radicals (•OH), and superoxide anion radicals (O₂•⁻). In the broiler feeding trial, the FRSM-5 group had significantly higher average daily gain (ADG) during the periods of 22–42 d and 1–42 d (p < 0.05), along with a significantly lower feed to gain ratio (F/G) (p < 0.05), compared with the CON and RSM-5 groups. Compared to the CON group, the FRSM-5 group showed a significantly higher slaughter rate (SR), full eviscerated rate (FER), and breast muscle rate (BMR) (p < 0.05), whereas the RSM-5 group had significantly lower SR and FER (p < 0.05). The activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in the serum and liver of the FRSM-5 group were significantly higher than those in the CON and RSM-5 groups (p < 0.05), and the serum immunoglobulin (IgA, IgG, and IgM) levels were significantly elevated (p < 0.05). Furthermore, compared with the CON and RSM-5 groups, the FRSM-5 group exhibited a significant increase in duodenal villus height (VH) (p < 0.05), a significant reduction in duodenal crypt depth (CD) (p < 0.05), and a consequent significant increase in the VH/CD (p < 0.05). In conclusion, microbial fermentation effectively enhances the nutritional value of RSM by improving its nutrient composition and reducing antinutritional factors. Replacing 5% SBM with FRSM in broiler diets significantly improves growth performance, enhances antioxidant capacity and immune function, and optimizes intestinal morphological structure, thereby replacing part of the soybean meal in broiler diets.

Peptidoglycan (PGN) is a unique component of prokaryotic cell walls with immune-enhancing capacities. Here, we extracted PGN from Corynebacterium glutamicum, a by-product of amino acid fermentation, using the trichloroacetic acid (TCA) method. SDS-PAGE analysis confirmed the presence of PGN, with a band of approximately 28 kDa. Further analysis was conducted through amino acid analysis, FTIR, and MALDI-TOF/TOF MS, and the results showed that the chemical structural monomer of PGN is NAG-(β-1,4-)-NAM-l-Ala-d-Glu-l-Lis-d-Ala. The immune activation effects of PGN were evaluated in a RAW264.7 cell model. Our results showed that PGN could increase the secretion level of NO, ROS, and immune regulatory substances, including TNF-α and IL-1β, and up-regulated the mRNA expression of TNF-α and iNOS. In addition, PGN stimulated the expression of ERK2, MyD88, RIP2, and the related receptor NOD1 in the NF-κB and MAPK pathways. Comparative RNA sequencing was conducted to analyze the gene expression profiles in RAW264.7 cells. KEGG analysis indicated that most of the genes were enriched in the NF-κB, MAPK, and TNF signaling pathways. Taken together, these findings suggest that PGN may have immune-activating potential for the development and application of immune adjuvants. Importantly, the application of PGN also provides a new way to utilize amino acid fermentation by-products.